Sales Tax Total
Price after adding a percentage tax.
Formula
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Example
$50 + 10% tax = $55
How it works
This formula finds the final price by adding a tax percentage to the original price. The fraction t/100 turns the tax rate into a decimal share of the pre-tax price, and multiplying by N gives the tax amount itself. Adding that tax to N is the same as multiplying N by 1 + t/100, which combines the original cost and the extra charge in one step.
When to use it
Use this when you know the price before tax and the sales tax rate, and you need the amount owed at checkout. It applies to shopping, invoices, receipts, and any basic price-plus-tax calculation.
Worked example, step by step
Pre-tax price: N = $80 Tax rate: t = 7.5% Convert the tax rate to a decimal factor: 7.5/100 = 0.075 Compute the total: total = 80(1 + 0.075) Total = 80(1.075) Total = $86
Common mistakes to avoid
- Using the tax percent as a whole number without dividing by 100
- Adding the tax rate directly to the price instead of calculating the tax amount first
- Subtracting tax instead of adding it when finding the final total
Did You Know?
Sales tax is added at the register in the US, but most of the world quotes VAT-inclusive prices — so the sticker is what you pay.
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